I just got off the phone. My notes said we were finding broken heads because evidently, some of those heads didn't have the dowel hole drilled deep enough. That dowel pin would hold the head off the deck and crack the head under the port above the bolt holes.
If you have a leak between the head and the block and the head isn't cracked, you may have a dowel that is just a skosh long and is holding that end of the head up enough for a leak and not fracture the casting.
I knew there was a reason we were seeing those heads fracture.
Hope this gives you something to look at.
